Beijing 2008 has its bird's nest stadium and Wembley its soaring arc of light, but the organisers of London 2012 revealed a rather more cautious design today, when they unveiled plans for their Olympic stadium.

"This is not a stadium that's going to be screaming from the rooftops that it's bigger and more spectacular," admitted its chief architect, Rod Sheard. "This is just a cleverer building. This is a cleverer solution."

Organisers hope to ensure the coliseum-style stadium, which will be built in Stratford, east London, can continue to be used on a smaller scale after the Olympics, by scaling down its 80,000 capacity to 25,000 in the months following the Games. It will then become a multi-purpose venue with athletics as a major use, but no anchor tenant, such as a football or rugby club, has been found.

"This is a very important Olympic milestone and this stadium is focused very much on legacy and sustainability," said the Olympics minister, Tessa Jowell. "Once the Games are over this will then be translated into a stadium that will not only host grand prix athletics events and other national sport events but will also serve the communities of the boroughs."

Lord Coe, chairman of the London Organising Committee, agreed that the stadium's long-term use was an important factor in the design. "It's a stadium that delivers on everything we said we would deliver on," he said. "A stadium with track and field as its primary legacy; a stadium that will be reduced from 80,000 seats in Olympic mode to a 25,000-seater community base."

The permanent seating in the stadium will be built on a concrete bowl sunk into the ground. The architects hope this design will bring spectators closer to the action and create an electric atmosphere. "We've ended up with a very tight, very compelling bowl," said Sheard. "The atmosphere inside this bowl, we think, will be pretty special."

The stadium will also boast a cable-supported roof, providing cover for two-thirds of spectators, and a fabric curtain that will wrap around the structure, acting as additional protection and shelter for spectators.

The £496m structure has nearly doubled in budget from the £280m estimated in 2004 when London was bidding for the Games. David Higgins, the chief executive of the Olympic Delivery Authority, has blamed the spiralling costs on VAT and inflation.

With half an eye on the fiasco surrounding the delayed construction of the new Wembley, building work on the stadium is set to begin three months ahead of schedule in April 2008, with completion in 2011 to allow for test events. So far, 20 out of 33 buildings on the site have been demolished and 600,000 tonnes of soil taken away in preparation for the construction process.